In downlink, it is necessary to multiply channels by scrambling codes to randomize other-cell interference. In W-CDMA downlink, all types of physical channels other than the synchronization channel (SCH) are multiplied by a common scrambling code that is unique to each sector. Here, a sector indicates each sub-area of an area (cell) covered by one base station. Currently, the long term evolution (LTE) standard, which is an advanced version of the W-CDMA downlink high-speed data communication standard, is being developed to implement high-speed, high-capacity mobile communications. Scrambling codes are also important to randomize other-cell interference in evolved UTRA (E-UTRA) that is a radio access scheme in LTE.
For example, a method of assigning scrambling codes to physical channels in E-UTRA downlink using OFDM is disclosed in R1-060036, “Scrambling Code in E-UTRA downlink,” 3GPP TSG-RAN WG1 LTE Ad Hoc Meeting, Helsinki, Finland, Jan. 23-25, 2006. In the disclosed method, the pilot channel and the broadcast channel (BCH), such as a reference signal and broadcast information, are always multiplied by a cell-specific (base-station-specific) scrambling code and sector-specific orthogonal sequences to orthogonalize downlink channels of different sectors. Also, the paging channel is multiplied by a cell-specific (base-station-specific) scrambling code. Further, shared data channels and layer1/layer2 (L1/L2) control channels are multiplied by a combination of a cell-specific (base-station-specific) scrambling code and an orthogonal sequence when the channels are to be spread or are multiplied by a combination of a long scrambling sequence and a cell-specific (base-station-specific) scrambling code when the channels are not to be spread.